If event seats are full, user can't change RSVP to "Not attending"

Hi there,

if I set in event options available seats, when people give RSVP to Attend, and amout of available places is full, user can't change RSVP to "Not attending", because when he click RSVP button in eent view, he will see information "Sorry, there are no more seats available for this event" instead of option "Not Attending".